Techniques for the fabrication of field effect transistor (FET) devices are well known to those skilled in the art. For a conventional planar device, the process for device fabrication will typically form a gate stack over a substrate and then use the gate stack as a mask for the implantation of the source-drain regions on either side of the gate stack. It is further known in the art to subsequently use epitaxial growth to produce raised source-drain regions. The gate stack may comprise the actual gate electrode (as known in a technique referred to as “gate first” fabrication) or comprise a dummy gate (as known in a technique referred to as “gate last” or replacement metal gate (RMG) fabrication).
As the technology node continues to shrink, the scaling of the FET devices requires higher mobilities in the transistor channel region. Additionally, aggressively scaled FET devices further require a very sharp junction between the source-drain region and the channel region. The conventional processes described above for device fabrication, however, have a number of issues which become more significant as device sizes shrink. For example, it is difficult to provide a fully strained channel with high mobility for both n-channel and p-channel devices. Another issue concerns the formation of diffused junctions which degrade short channel control. Another issue with diffused junctions is an increase in resistance in the extension region of the transistor device resulting in reduced device performance. Another issue relates to pitch scaling which can introduce challenges in block level patterning. It is also recognized that resist residues at tight pitches necessitate the use of high energy extension implants, and these implants can worsen the diffused junction concerns noted above.
A need accordingly exists in the art for an improved transistor device manufacturing process that addresses the foregoing and other issues and provides a high mobility channel region and a sharp junction between the source-drain region and the channel region.